The present application relates to a shielded power coupling device configured to transfer electric power between a rotating object (e.g., a rotor) and a stationary object (e.g., a stator) and/or between two rotating objects. It finds particular application in the context of computed tomography (CT) scanners, such as might be used in medical, security, and/or industrial applications. For example, the shielded power coupling device may be configured to transfer electric power from a stationary portion to a rotating gantry that houses a radiation source and a detector array. It also relates to other applications where a power coupling device that reduces RF emissions and/or other electromagnetic interferences, reduces leakage inductance, and/or improves efficiency during inductive transfer of electric power may be useful.
Systems that comprise electronic components within a rotating unit often require power to be provided to the rotating unit via a power coupling apparatus. For example, in CT scanners, power is supplied to electronics on a rotating gantry of the CT scanner using a power coupling device. Traditionally, these power coupling devices have been slip-ring/brush assemblies. Slip-rings transfer electricity between a stationary member and a rotating member (e.g., or between two rotating members), through the contact of two materials (e.g., via a sliding contact). Slip-ring assemblies typically comprise two or more continuous conducting rings and one or more brushes on respective rings for delivering current to and from the rings.
Ordinarily, numerous slip-rings are used in order to supply different voltage levels to electronic components of the rotating unit (e.g., as required by the various electronic components of the rotating units). While the use of brushes and slip-rings has proven effective for supplying power to electronics comprised in a rotating unit, conventional brush and slip-ring mechanisms tend to be dirty, unreliable, and/or noisy. For example, the brushes can break down to create metallic dust overtime, which may cause problems with ultra-sensitive electronics. Moreover, in some applications, such as where sensitive diagnostic/imaging procedures are being performed (e.g., such as in CT imaging), the electric noise inherent in the power being transferred and/or generated by the brushes can cause interference with the procedures. Other drawbacks of slip-ring assemblies include the cost and complexity of manufacture due to the special materials and/or the mechanical precision that is generally required.
Numerous solutions have been proposed to transfer power to electronic components of a rotating gantry without using slip-rings. For example, U.S. Pat. No. 4,323,781 to Baumann discloses an inductive transformer for transmitting energy to an x-ray tube in a rotatable CT-scanning system. The inductive transformer in the Baumann patent consists of primary and secondary windings. An alternating current passing through the primary winding induces a current in the secondary winding. The primary winding is stationary with respect to the scanning system, whereas the secondary winding rotates with the scanning system and provides power to the rotating x-ray tube.
U.S. Pat. No. 4,912,735 to Beer discloses a similar concept, namely a power transfer apparatus including two concentric rings mounted on a static member and a rotating member, respectively. The rings have opposed annular faces, respectively containing a groove. Conductive windings in respective grooves provide an inductive coupling means for coupling power to the rotating gantry in the CT scanner. U.S. Pat. No. 5,608,771 to Steigerwald applies a substantially similar concept to a quasi-resonant high voltage generation scheme.
Although the devices discussed above allow for power transfer to rotating systems without the need for slip-rings, they suffer from a number of drawbacks. For example, these devices do not provide to the user the flexibility of transferring power between a plurality of input and output voltages as is useful in some applications, such as in CT scanners. Further, these solutions provide few options to the user for adjusting the current and voltage in the power transfer device so as to achieve a desired (e.g., optimal) power transfer efficiency. Moreover, it will be appreciated that these solutions do not consider shielding. The lack of adequate shielding may, for example, result in undesirable RF emission, which may be particularly undesirable in applications that are sensitive to such results, such as CT scanners, for example.